Railway Traction, Power and Energy

Is it possible to take a fleet of existing mid-life UK Diesel Multiple Units and sensibly convert them to run on hydrogen fuel cells? This study undertaken in conjunction with Hitachi Rail Europe and Fuel Cell System Limited, sponsored by the UK Rail Safety & Standards Board came to the conclusion that:

It is technically possible using existing technology;

There would be a substantial improvement in performance and a range sufficient to allow daily refuelling;

Fuel costs would be dramatically reduced;

There would be a significant reduction in CO2 emissions and other pollutants;

All at a fraction of the cost of electrification.

For many UK branch lines, this could be a good solution to provide a cleaner, faster, quieter journey than diesel, without the expense and disruption associated with electrification.

What is the most cost-effective way of powering the UK train fleet into the future? This award-winning dissertation by Giles Pettit of SNC Lavalin looked at where the gaps are going to be once the UK completes its current planned electrification, and then took the East Midlands area as a case study, and evaluated the following rolling stock options over a 60 year period:

The cost of electrifying the entire franchise area, and running exclusively EMUs;

Doing no further electrification, and using Bi-Mode DMUs that pick up power from overhead wires where available and have diesel generators for everywhere else, as per the UK's new fleet of Hitachi IEPs;

Doing no further electrification, and using Independently Powered Electric Multiple Unites (IPEMUs) that used the overhead wires to charge up sizeable battery packs for use on non-electrified sections of line, as per the recent class 379 IPEMU demonstrator that ran in-service last year;

Doing no further electrification, and using a Bi-Mode Fuel Cell Electric Multiple Unit (Bi-Mode FCEMU) powered by the overhead where available, but which has a hydrogen fuel cell allied to a much smaller battery to enable it to run partly or continously on non-electrified line (like Alstom's new Coradia iLint, but with an additional pantograph).

There looks to be considerable savings for the IPEMU and FCEMU options when considering whole life cost.

Railways are facing increasing pressure to provide more intelligent power management strategies. This paper presents an integrated optimisation method for metro operation to minmise substation energy consumption by calculating the most appropriate train trajectory and timetable configuration. The results show that:

The algorithm considers all the trains running in the whole network throughout the whole day operation;

The method is able to improve the driving strategy and train regenerative braking energy efficiency;

The optimal timetable is able to reduce the substation load, which improved the reliability of the railway power network and coould reduce the substation investment cost.

The integrated optimisation is able to improve overall metro performance and reduce the energy consumption.

For metro-transit systems with frequently motoring and braking trains, the effective use of regenerated braking energy is a significant way to reduce the net energy consumption. Although eco-driving strategies have been studied for some time, a comprehensive understanding of how regeneration affects the overall system energy consumption has not been developed. This study will address the that:

A mutli-train traction power network simulation which is able to evaluate the energy flow of the whole railway network;

The energy consumption evaulation on existing systems, and suggestions in potential energy-saving methods;

The approach to improve the efficiency of regenerative braking energy usage;

Various optimisation algorithms to improve the driving strategy and timetable for system energy saving

A case study has been carried out in Beijing Yizhuang Subway Line, 38% of the energy consumption from substations can be reduced.

Train trajectory optimisation plays a key role in improving energy saving performance. However, very few of the optimisation results have been evaluated and rested in practice. This paper presents a field test of an optimal train trajectory on a metro line to evaluate the practicability of the trajectory. The results show that:

Implementing an optimal trajectory in practice could successfully reduce the train actual energy consumption by up to 19% on a Beijing Metro Line;

The train trajectory of the actual optimal operation is similar to the simulated optimal operation one;

The human driver is able to follow the instructions from the driver advisory system.

It can be concluded that implementing the optimal train trajectory is both practicable and convenient, and it could help the train operator to significantly reduce energy costs.